1. Field of the Invention
This invention relates to an audio system which uses a plurality of analogical acoustical assemblies in combination to thereby provide a sound space capable of obtaining good sound reverberation with an average sound absorbing coefficient of 0.1 to 0.5.
2. Description of the Prior Art
Recently, acoustical assemblies used for sound absorption, reflection and sound-shields have been, as shown in FIG. 9, suitably arranged in a room to realize a sound space with an average sound absorbing coefficient of 0.1 to 0.5, and this is becoming the standard in audio related industries.
Under such a circumstance, an audio system having a speaker system for reproducing sound, a sound absorption system for absorbing sound, a reflection system for reflecting and diffusing sound and a sound shield system for shielding sound provided on the same cabinet has been disclosed in Japanese Laid-Open Patent Application No. 2-201498.
A listening room or the like to be used for an audio application employs a sound absorption material in order to control sound reverberation. As the sound absorption material to be used for this purpose, an absorbing layer made of porous material such as glass wool, rock fiber, cellular plastic or the like is known, which will be explained by referring to the drawings.
Conventionally, a surface of a wall is formed by arranging the sound absorption material 91 and a reflection cabinet 94 in the same or analogical shape on a surface of a front surface baffle of a reflection cabinet 92 as shown in FIG. 9. The reflection cabinet 94 has a projection 93 having a quadrangular pyramidal form to reflect sound in a direction of a projection surface. By forming a space by the surface of the wall, a sound reproducing space such as that shown in FIG. 9 is realized.
However, the sound absorption material 91 shown in FIG. 10 has a limitation in the frequency of sound to be absorbed, due to a material characteristic which is determined depending on a thickness of the absorbing layer made of porous material such as glass wool, rock fiber or cellular plastic. On the other hand, a thickness of the wall is about 8 to 15 cm, for example, in the case of a partition. In such case, a thickness of the sound absorption material ranges from 5 to 10 cm. As shown in FIG. 11, frequency response of sound to be absorbed of the absorbing layer made of porous material is such that when the frequency is low, a sound absorbing coefficient is small and when the frequency is high, the sound absorbing coefficient is large. As a result, in order to realize the desired sound adsorptive condition, the sound absorbing coefficient of the surface of the wall may be made large. Accordingly, if the thickness of the sound absorption material is made large, the sound absorbing coefficient of a low frequency sound becomes large and at the same time, the sound absorbing coefficient of a high frequency sound also becomes large. In addition, even when an area of the sound absorption material 91 shown in FIG. 12 is increased to make a sound absorption area large, a sound absorption characteristic of such a room becomes high in the high frequency range as shown in FIG. 13 due to the fact that the high frequency sound and the low frequency sound are different in equivalent absorption area from each other.
Also, a multilayered sound absorption material is known which is formed of plural sound absorption materials providing air layers therebetween. It becomes thick structurally because of the provision of the air layers therebetween, so that thickness of the sound absorption material ranging from 5 to 10 cm cannot be realized. The thickness of the sound. absorption material is only increased specifically, so that the sound absorbing coefficient for the low frequency sound becomes large and at the same time, the sound absorbing coefficient for the high frequency sound also becomes large. As a result, the sound absorbing coefficient for the high frequency sound becomes higher, thus making it difficult to realize a sound absorber having a constant sound absorbing coefficient. Accordingly, the reverberation time of the room becomes long for the low frequency sound and short for the high frequency sound. Consequently, the low frequency sound is not absorbed and diffused, so that a desired reverberation characteristic cannot be obtained, or standing waves and/or echo problems cannot be removed.
Also, a sound shield panel which absorbs the high frequency sound, and reflects and transmits the low frequency sound is disclosed in U.S. Pat. No. 3,628,626. An object of this panel is that the high frequency sound is absorbed as much as possible and the low frequency sound is reflected by an inner layer metal plate to thereby prevent the sound from being leaked outside from a partition. As a result, acoustic characteristics of an inside space divided by the partition cannot be controlled for all frequencies of the sound range.